This invention relates to an electronic tone generator for producing melodies.
Examples of conventional electronic tone generators are disclosed, for example, in Japanese Patent Publications No. 62-35117 and 63-19880 as well as U.S. Pat. No. 4,273,019.
FIG. 10 is a block diagram of a conventional electronic tone generator of this type. The generator shown comprises a basic-pulse generating section 101 for generating basic pulses having a period representative of the shortest duration of a musical note used in constructing the melody, a scale-pulse generating section 102 for generating scale-generating pulses, scale generating sections 111 and 111' for generating a plurality of (for example, two) types of scale data, a plurality of (for example, two) waveform generating sections 107 and 107' for generating melody-waveform signals corresponding to the respective types of scale data generated in the respective scale generating sections 111 and 111', on the basis of these types of scale data, a mixing section 108 for mixing the melody-waveform signals generated in the waveform generating sections 107 and 107' with each other, an amplifying section 109 for amplifying the mixed signals, and an output section 110 for outputting the amplified signals after converting them into an acoustic signal.
The scale generating section 111 is adapted, for example, to generate the scale of a main melody, and comprises a storage circuit 105 for storing the scale data and tone-length data on the main melody, an address counter 104 for specifying addresses in the storage circuit 105, a programmable counter 103 adapted to receive tone-length data output from the storage circuit 105 and to generate tone-lengths by dividing basic pulses generated by the basic-pulse generating section 101, and a programmable counter 106 adapted to receive scale data output from the storage circuit 105 and to generate scales by dividing scale-generating pulses generated by the scale-pulse generating section 102.
The scale generating section 111' is adapted, for example, to generate the scale of a sub-melody, and comprises a storage circuit 105' for storing the scale data and tone-length data on the sub-melody, as well as an address counter 104' and programmable counters 103', 106', which have functions similar to those of the address counter 104 and programmable counters 103, 106, respectively.
In an electronic tone generator having the above-described construction, the scale signals for the main melody and sub-melody are generated on the basis of the scale data and the tone-length data stored in the storage circuits 105 and 105'.
The scale signals thus generated are input to the waveform generating sections 107 and 107', where they are waveform-processed into a main-melody-waveform signal and a sub-melody-waveform signal and are output to the mixing section 108 The mixing section 108 mixes the main-melody-waveform signal with the sub-melody-waveform signal, and the mixed signals can be output in the form of an acoustic signal through the amplifier 109 and the output section 110.
Furthermore, in the conventional electronic tone generator described above, an envelope waveform is imparted to melody-waveform signals with a view to generating an electronic tone spreading widely, which provides high acoustic and musical effects.
However, the conventional electronic tone generator is equipped with separate scale generating sections 111 and 111' so that it may simultaneously generate tones of different (for example, two) scales, and, in particular, it requires a plurality of storage circuits 105, 105', address counters 104, 104', and programmable counters 103, 103', the address counters 104, 104' requiring synchronization
As a result, the size and construction of the circuit becomes larger and more complicated as the number of kinds of scales to be simultaneously generated increases, which means there is a limitation to the reduction in the size and price of the generator. Furthermore, when realizing this electronic tone generator in a single integrated circuit, it is rather difficult to arrange the entire generator in a more compact form in the integrated circuit since the circuit for imparting an envelope waveform is formed as an analog circuit arranged externally with respect to the integrated circuit.
In addition, the conventional electronic tone generator can merely output a rather monotonous tone which consists of a mixture of a main melody and a sub-melody only, and is not capable of outputting a tone providing a remarkably high musical effect.